Scientific instruments, such as spectrometers, collect raw data (for example, in the form of a number of counts per second) that can be used to determine characteristics of a measured sample. The raw data needs to be processed to provide useful calculated results. Algorithms are therefore developed, as needed, to analyze raw data generated by instruments. The algorithms are typically developed by engineers who develop the instruments, and often require several months to develop.
Photoelectron spectroscopy is a technique used to determine the composition, thickness, profile, and etc. of elemental species in a sample. Photoelectron spectroscopy measures photoelectrons that are emitted by a sample that has been bombarded by monochromatic sources of radiation. For example, the sample may be bombarded with x-ray or ultraviolet radiation having a specific, predetermined wavelength. When the individual atoms of the sample absorb the photons of the radiation, the atoms emit an electron having a kinetic energy (KE) characteristic of the atom. This electron is known as a photoelectron. The photon absorbed by the atom has an energy e=hν, where h is Planck's constant and ν is the frequency of the photon. The photoelectron was once bound to the emitting atom. The binding energy (BE) of the photoelectron is the amount of energy required to strip the photoelectron from the atom. The KE measured by the equipment is the amount of energy the photoelectron has after being emitted. Because of the law of conservation of energy, it can be determined that KE=hν−BE. As the BE for an electron in an atom has a known value, if the wavelength of the photon striking the sample is known, the KE of an emitted photoelectron can identify the species of the atom.
The emitted photoelectrons can be counted using an electron energy analyzer. A spectrum plotting the number of photoelectrons counted at specific kinetic energies can be generated from the raw data. The spectrum can then be used to determine various characteristics of the sample, such as the chemical composition or the thickness.
Characteristics of the sample can be determined or calculated using the spectrum. However, in order to determine useful information about the sample, a specific algorithm for the specific sample and the desired characteristics must be formulated for each new sample and for each new set of characteristics to be determined. Developing the algorithms is often time-intensive and can retard the progress of analyzing the sample.